[dragonwriter]

> Isn't crystal lang trying to do the same thing?

Nope, Crystal is a statically-typed language with distinctly different than Ruby semantics that features Ruby-ish syntax.

Sorbet is an optional static type system for Ruby.

They aren't trying to do the same thing. One is trying to appeal to the aesthetic preferences of developers who like Ruby with static typing, the other is trying to enhance the Ruby ecosystem with static typing. There's only a superficial similarity between these things.